Technical Field
This disclosure relates to precision metrology, and more particularly to sensing configurations in probes used with coordinate measuring machines.
Description of the Related Art
Coordinate measurement machines (CMM's) can obtain measurements of inspected workpieces. One exemplary prior art CMM described in U.S. Pat. No. 8,438,746, which is hereby incorporated herein by reference in its entirety, includes a probe for measuring a workpiece, a movement mechanism for moving the probe, and a controller for controlling the movement. A CMM including a surface scanning probe is described in U.S. Pat. No. 7,652,275, which is hereby incorporated herein by reference in its entirety. As disclosed therein, a mechanical contact probe or an optical probe may scan across the workpiece surface.
A CMM employing a mechanical contact probe is also described in U.S. Pat. No. 6,971,183 (the '183 patent), which is hereby incorporated herein by reference in its entirety. The probe disclosed therein includes a stylus having a surface contact portion, an axial motion mechanism and a rotary motion mechanism. The axial motion mechanism includes a moving member that allows the contact portion to move in a central axis direction (also referred to as a Z direction or an axial direction) of the measuring probe. The rotary motion mechanism includes a rotating member that allows the contact portion to move perpendicular to the Z direction. The axial motion mechanism is nested inside the rotary motion mechanism. The contact portion location and/or workpiece surface coordinates are determined based on the displacement of the rotating member and the axial displacement of the axial motion moving member.
Motion mechanisms and/or conventional displacement detector arrangements such as those disclosed in the '183 patent may be relatively expensive and/or susceptible to various “cross coupling” errors due to mechanism and/or detector imperfections. A need exists for a sensing configuration in a probe wherein the displacement detector arrangements may be relatively less expensive while also rejecting various “cross coupling” errors despite reasonably expected mechanism and/or detector imperfections.